This proposal aims to examine the role of enriched environment in modulating anxiety-like behavior. Enriched environment has previously been shown to have major effects on brain morphology and function, including hippocampal neurogenesis and 5HT1A receptor (5HT1AR) expression. Our preliminary data suggest that enriched environment also alters anxiety-like behavior. In addition, our lab has shown that the 5HT1AR and hippocampal neurogenesis play a role in altering anxiety-like behavior. Therefore, we hypothesize that the effects of enriched environment on anxiety-like behavior are mediated by an activation of 5HT1ARs, which in turn triggers an increase in hippocampal neurogenesis. To test this hypothesis we will first reconfirm our preliminary data that show enrichment decreases anxiety-like behavior. Then we will assess the effects of enriched environment in mice that lack the 5HT1AR and in mice that have been hippocampally x-irradiated to block neurogenesis. With the knowledge gained by these experiments we will have a better understanding of the molecular and cellular basis of anxiety-like behavior.